The symptom of popping or snapping in the knee can be a sign of a few different problems. One of the key distinguishing factors is whether or not the popping or snapping causes or is associated with pain. Popping or snapping not associated with painful symptoms is often not a sign of a significant problem.
Patients may experience a symptom of popping called a "mechanical symptom." This may feel as though something is caught within the knee and is popping as the knee bends back and forth.1
This type of popping symptom is often a sign of a meniscus tear or a loose piece of cartilage within the joint.1 The torn meniscus or loose cartilage may catch in the knee as it moves back and forth causing a popping sensation.
While some meniscus tears heal on their own, those involving deeper tissue lack blood vessels to aid in the healing and may require a minimally invasive arthroscopic debridement to trim and repair the tear.
There are times when swelling of tendons that surround the knee can cause the tendons to catch on the knee as the knee bends. The most common type is called iliotibial (IT) band tendonitis. It occurs when the iliotibial band becomes swollen and irritated, and then catches of the end of the thigh bone as the knee bends back and forth.3
Unlike the mechanical popping where something is deep inside the joint, this type of popping is felt just below the level of the skin. Often the tendon can be felt by simply bending the knee back and forth with the hand resting on the affected tendon.